1. Field
Example embodiments relate to thin film transistors (TFTs), and in particular, to TFTs in which flatness of a surface of an electrode is improved when the electrode is formed by ink-jet printing.
2. Description of the Related Art
Thin film transistors (TFT) are used in various applications, for example, as a switching device and a driving device of liquid crystal displays (LCDs) and displays using organic light-emitting diodes (OLEDs), and as a selection switch of a cross point-type memory device. Currently, LCDs are widely used as a television (TV) panel, and OLEDs are being researched for use in TVs.
Generally, large-sized TVs or digital information displays (DIDs) should be produced at low cost and with high image quality (in terms of motion picture expression, high resolution, brightness, a black and white ratio, and color reproduction). A TFT should be suitable for use as a switching and driving device of a high performance display formed using large-size substrates of, for example, glass.
TFTs are formed by using a conventional photolithography process. However, the conventional photolithography process is a relatively intricate process, in which a photoresist (PR) is used and removed, and a conductive material or a semi-conductive material is deposited and a portion of the deposited material is removed. Due to high material consumption, the conventional photolithography process is environmentally unfriendly.
As an alternative to photolithography, printing is used to manufacture a TFT, and use of printing is gradually increasing. Among various printing methods, ink-jet printing is widely used. However, when a conductive or semi-conductive material is ink-jet printed, a concentration of solute contained in an ink is greater at an edge of a printing region than any other portion of the printing region when a solvent contained in the ink evaporates. Such an effect is referred to as a ‘coffee stain’ effect. In the presence of a coffee stain effect, a level of flatness of the printing region is relatively low.